[PATCH 3.2 20/77] mac: validate mac_partition is within sector

Ben Hutchings
2015-12-24T15:45:18Z

From: Kees Cook <keescook@chromium.org>

commit 02e2a5bfebe99edcf9d694575a75032d53fe1b73 upstream.

If md->signature == MAC_DRIVER_MAGIC and md->block_size == 1023, a single
512 byte sector would be read (secsize / 512). However the partition
structure would be located past the end of the buffer (secsize % 512).

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jens Axboe <axboe@fb.com>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/partitions/mac.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

--- a/fs/partitions/mac.c
+++ b/fs/partitions/mac.c
@@ -32,7 +32,7 @@ int mac_partition(struct parsed_partitio
Sector sect;
unsigned char *data;
int slot, blocks_in_map;
- unsigned secsize;
+ unsigned secsize, datasize, partoffset;
#ifdef CONFIG_PPC_PMAC
int found_root = 0;
int found_root_goodness = 0;
@@ -50,10 +50,14 @@ int mac_partition(struct parsed_partitio
}
secsize = be16_to_cpu(md->block_size);
put_dev_sector(sect);
- data = read_part_sector(state, secsize/512, &sect);
+ datasize = round_down(secsize, 512);
+ data = read_part_sector(state, datasize / 512, &sect);
if (!data)
return -1;
- part = (struct mac_partition *) (data + secsize%512);
+ partoffset = secsize % 512;
+ if (partoffset + sizeof(*part) > datasize)
+ return -1;
+ part = (struct mac_partition *) (data + partoffset);
if (be16_to_cpu(part->signature) != MAC_PARTITION_MAGIC) {
put_dev_sector(sect);
return 0; /* not a MacOS disk */